Well, you kind of already hit it on the head: spaying will help with the odor; anything else is just covering it up, at best.. I know that money can be tight, and there is no good way to say this, but rabbits can be expensive pets to have.
I learned the hard way about GI stasis, but in addition to stasis, rabbits can also be prone to teeth problems as well as other problems. Why I am saying this is that somehow you will need to have a vet fund on hand for emergencies; with rabbits, there is a good chance one will arise.
Additionally, an unspayed rabbit (like unspayed rats and other animals) have a much higher chance of reproductive problems later in life, and you will not only be facing $$$ then but emergency surgery on an older animal, a situation that is much more expensive and much more dangerous for your rabbit.
Back to the problem at hand: I would look around or ask your local House Rabbit Society if they know of a reasonably priced rabbit savvy vet: http://www.columbusrabbit.org/
It is important to find a vet that works with rabbits; not all vets are familiar with their sensitive systems. Here is a list of the Colombus OH's HRS vet list, there are a good amount on it:http://www.columbusrabbit.org/vets.php
This is a good time of year to see if people will make donations to your vet fund in lieu of holiday presents! That is one way you can start a fund.